18-12 Class #18 Optional Material Part A - Kepler’s Laws of Orbits Material on Kepler’s Laws thanks to Professor Dan Sperber
18-13 Kepler’s Three Laws of Planetary Motion 1. The Law of Orbits: All planets move in elliptical orbits having the Sun at one focus. 2. The Law of Areas: A line joining any planet to the Sun sweeps out equal areas in equal times. 3. The Law of Periods: The square of the period of any planet about the Sun is proportional to the cube of the semi-major axis of its orbit.